It wouldn't be Star Trek (TOS), not that it really was. TNG took place over 80 years after the events of TOS, of course it looked more advanced.

This is Kirk, Spock and McCoy, their place and point in time in Star Trek history is basically set in stone now. To change it would mean you are not making Star Trek any more.

TNG had to, they're the future; the current movie is the time-line of the original Trek; they can't do that, it wouldn't make sense.

The new movies were backward thinking by design. Into Darkness takes place 5 years before TOS and 100 years before TNG. Any radically new federation technology inserted there but not shown in TOS/TNG would just look out of place and be held against it.

They couldn't create tech that was TOO forward thinking, IE creating tech that might be seen around the time of TNG - given that as a franchise they could still mine a reboot of TNG if the well for Kirk-era Star Trek runs dry.

I wasn't disappointed by the tech. To be frank, I think that they're simply giving themselves room to continue making money with rebooting other Star Trek franchises in the future